1. Field of the Invention
The present invention relates to an improvement of a flywheel device, in which a flywheel assembly includes: a mass-side rotor including a mass ring and a pair of holder plates having outer peripheral portions connected to the mass ring with the mass ring sandwiched therebetween; a driven plate which includes an output hub disposed coaxially with the mass ring and which is disposed between the holder plates rotatably relative to the holder plates; and a torque damper interposed between the holder plates and the driven plate, the mass-side rotor is connected to a crankshaft with a drive plate therebetween, and positioning means for positioning the mass-side rotor and the drive plate coaxially with each other is provided between the mass-side rotor and the drive plate.
2. Description of the Related Art
Such a flywheel device is already known, for example, as disclosed in Japanese Patent Application Laid-open No. 2005-188661.
In such a conventional flywheel device, an annular positioning protrusion and an annular positioning recessed portion to be fitted to each other are formed on surfaces facing to each other of the drive plate and the mass ring as positioning means for positioning the mass-side rotor and the drive plate coaxially with each other. However, since the mass ring is generally forged or cast, the formation of the positioning protrusion or the positioning recessed portion therein requires a complicated forming die or cutting after the forging or casting, each of which is a factor inhibiting the reduction in production costs. Moreover, when the mass of the mass ring is increased along with the change in specification of the flywheel device, holder plates and the like to be connected thereto need to be manufactured newly. As a result, the mass productivities of components are reduced, which is also disadvantageous in terms of costs.